Project Summary Unlike proteins and small-molecules, hybrid nanoparticle assemblies are never atomically precise and therefore have non-uniform composition and size. This fundamentally limits the researcher's ability to precisely engineer recognition and binding properties of these assemblies. This is especially true of a large class of hybrid noble metal nanoparticles including gold-based systems (AuNPs). Weak metal-ligand interactions contribute to a statistical distribution of defects and positional uncertainty of ligands around the metal core, limiting their molecular precision. Consequently, inherent polydispersity features of hybrid nanoparticles leads to their diminished selectivity when they are designed to target and bind biomacromolecules. Furthermore, under relatively benign conditions, weak metal-ligand interactions in the hybrid nanoparticles can result in scrambling events and ultimately degradation. Therefore, the status quo in the field largely centers on our inability to rationally address structure-function properties of hybrid nanomaterials. Our proposed effort can be characterized as a ?nanoparticle total synthesis?, where we are utilizing a bottom-up approach for the synthesis of large hybrid molecules using atomically precise 3D inorganic clusters as rigid templates. Specifically, we propose a new strategy for building robust, atomically precise hybrid nanomolecules using air-stable inorganic clusters densely decorated with perfluoroaromatic functional groups. This strategy is very appealing given its similarity to the synthesis of AuNPs; however, in this case, the resulting structures maintain full atomic precision and exhibit dramatically improved stability due to the full covalency of the resulting systems. We will use this strategy for facile attachment of receptor building blocks and positioning these in three-dimensions with an atomic precision. For our studies, we will work on developing multivalent species capable of binding and sensing biomolecules under biologically relevant conditions. We will work to understand three-dimensional structures of our assemblies and how the size and dynamics in these systems affects ?perfect? target binding. Atomic precision of these species will enable us to conduct structural studies to precisely pinpoint these interactions. We will study a cooperative binding of the peptide-grafted clusters with multiple sub-components of the viral entry machinery; and show how an atomically precise nanomolecules grafted with oligonucleotides can be evolved as binders using in vitro selection. Ultimately, our work will help to promote a thorough understanding of the design rules governing interactions between hybrid nanomaterials and biomolecules and elucidate the dominant factors that enhance specific inhibition of complex biomolecular targets. For the first time, combining elements of inorganic cluster chemistry, chemical biology and materials science we will enable researchers to create well-defined programmable nanosystems with unique capabilities for binding and sensing complex biomolecules.